Accuracy question

[sambo_]

1 last thought... You said you've fired thousands of rounds rimfire. That's a big leap to 30-06. First marksmanship principle-position and hold must be firm enough to support the weapon. -Bigger gun, firmer hold for sure but I suspect your afraid of it somewhat and might be holding too tight as well as anticipating that shot way too much! (snatching). You shouldn't know when the shots going out the barrel but thats another lesson.

 

[Longwalker]

Shoot groups from the bench to gain confidence in your rifle. Shoot groups from hunting positions to gain confidence while hunting.
Boomer's advice is right on. Bench rest shooting is nearly useless as training for hunting.
Do you use good hearing protection? I find that I shoot much better when I'm not hurting my ears.
And nobody mentioned checking your mounts and rings for loose screws. Loose screws can drive you crazy - the rifle can be a very erratic shooter, or hold one "position" for a short while. Base screws should be treated locktite, rings properly torqued.